#include <iostream>
#include <cstring>
#include <cmath>
using namespace std;
#define PI 3.14
class Ellipse
{
private:
  int x, y, l_r, s_r;

public:
  Ellipse(int, int, double, double);
  double Area();
};

Ellipse::Ellipse(int x, int y, double l_r, double s_r)
{
  this->x = x;
  this->y = y;
  this->l_r = l_r;
  this->s_r = s_r;
}

double Ellipse::Area()
{
  return PI * l_r * s_r;
}

int main()
{
  int x, y;
  double l_r, s_r;

  Ellipse t(x, y, l_r, s_r);
  cout << t.Area() << endl;
  return 0;
}